Managing EGR for MPG
 

I understand why WAI helps fuel economy. Basically, it allows the engine to suck in a smaller mass of air into the engine throught a wider throttle setting. This reduces manifold vacuum, and therefore reduces engine pumping losses.

Another way to achieve the same effect could be by adding exhaust to the intake. First, exhaust is hot, so it would have an WAI effect. Secondly, it would reduce the O2 content of the intake, so less fuel would be added during closed loop operation.

EGR is often used to reduce NOx emissions. Has any Gassaver tested EGR for fuel economy?

I've also read a bit about this in the past month or so. At first glance it makes sense. Something worth looking into.

Understanding exhaust gas recirculation systems

https://www.asashop.org/autoinc/nov97/gas.htm

The only problem is the octane rating of gasoline, which limits the reduction in pumping losses available from EGR. The nice this is that excessive EGR used with light turbocharging and a fuel with high octane, like methanol or ethanol, results in better efficiencies than diesel engines obtain, with a fraction of the NOx production.

Even worse, North America has very low octane ratings vs. Europe. The average Octane rating is about 87, with 91-92 as the common high-end. There are pumps that offer 94 (Sunoco), and racing fuel pumps at 100, but both of those are expensive, and we don't have Sunocos here. I think they limit the rating because Xylene creates a cancer-causing pollutant when burned.

I think Utah and Colorado limit Octane in parts of the year -- if someone can confirm me on this.

But that's where the problem lies. I recall driving a '03 Ford Fiesta in Scotland that attributed great power and efficiency from its 1.2L engine to a higher compression ratio, as allowed by higher octane.

So then, without the addition of a mild-turbo, would modifying the EGR produce better FE and better emissions if altered in use? The linked article points to a complicated OBD-II computer system that gets the term of "Executive", that controls all of the "air breathin' gadgets".

The term conjures-up those old informational pamphlets, like "EGRs and You: How Does my Car's Emissions System Work???". There's a cartoon of this guy in a suit under the hood, taking reports from the board (EGR, O2 sensor, etc.) and making a decision, "OK, it's settled, we're going to make the air/fuel ratio richer at this point. Any new business? OK...so now what seems to be the trouble in the O2 sensor department...alright, EGR we need you to close slightly..."

For OBD-I or zero, it may be easier to fiddle with, as this complex feedback loop and processor isn't involved so much. May require a piggyback ECU or EIFE to program, if it's worth it.

RH77

I'd guess it would. The only things the turbo does are improving power in proportion to increased air flow and efficiency by a small bit. For any car it'd probably be easier to scrap the current ECU and run SAFI. In terms of price, methanol seems to vary widely depending on area, but supposedly it can go for ~$2 a barrel, which would make it competative with gasoline, especially when factoring in the increase in efficiency available.

Xylene, but CAREFULLY
 

When I had my Evo, the most cost-effective increase in octane was to open a "contractor's" account (free) at the local paint store chain, and buy Xylene by the 5-gallon container. I chose Xylene becuase of its availability, cost, and that oil companies already add it to their fuels to increase octane ratings. Also, if you buy anything else in bulk like Methanol or Acetone, you may get investigated as part of the "Meth-Watch" program as Methamphetamine production is rampant here in the MidWest (it has improved with the behind-the-counter Sudafed law). I'm not making Speed, only driving the car, so I don't have anything to hide. In addition, it was very difficult to find the purity of those other aromatics as Acetone had other distillates added, or you bought it very expensively from a Scientific/Chemistry supply outfit.

Now don't ask about Thanksgiving Day '03 and the "Great Xylene Spill Incident of Shawnee, Kansas" :thumbdown: -- it will "melt" rubber (read: tires, shoes, synthetic broom bristles, garage door seals, etc.) What a mess that was. The only solution was to contain it, blow fans on it, have it evaporate, and keep ignition sources away. Fire containment equipment was readied.

RH77

Xylene is some nasty stuff. I made the mistake of using it w/o gloves and boy did it itch. Something that someone may want to do is register their car as an alternative fuel vehicle with the state DMV if they have that designation, that way the feds can cross reference that info and hopefully stay off your back. I saw a story on the new behind-the-counter law, and they stated that most meth comes from out of country because it's cheaper to make it and ship it. Honestly, even if they suspect you of using it for illegal pruposes, the most they may do is have a heli buzz your place every now and then. My mom used to put up shade cloth for our dogs during the summer, and the police heli would buzz us once or twice a month, because dogs are weed. :rolleyes:

OK I have to ask
 

Alright I have to ask -- and it will lead somewhere, I promise. What does your Username stand for: Oh my God, What the F---, Bring Your Own Bar-B-Que? Judging by that, I would guess your location to be: Memphis, the Carolinas, Texas, or KC. Or I could completely be wrong. I'd fail miserable as a detective (except for the hot pursuits -- insert Roscoe P. Coltrane chuckle here).

RH77

You are right about the acronym, but even if the character count would allow it, it would still be in letter form. And you are wrong about location, but that's not reason not to guess. We've gotta be wrong to figure out what's right! :D

So what's the verdict? If I plumb some 3/8" copper tubing from the exhaust pipe to the intake manifold, will I see better mileage?

Probably not since the engineers who set-up your engine already figured the maximum amount of heated exhaust that could be added w/o raising the cylinder temp too much, i.e. egr is probably already optimized for fuel economy, unless you don't have it. You could try it, but make sure to keep an eye on the engine and have a cut-off you can use in the car, detonation is never good for an engine. A nice project would be to take a solid old iron block/head engine, retrofit it for SAFI/EGR, and run methanol. Maybe even a turbo if you're so inclined.

omgwtfbyobbq: are you sure you don't have things backward, re: cylinder temps with EGR present? (And related issues of detonation/octane)

The little reading I've done on EGR says that it lowers combustion temperatures (thus reducing formation of oxides of nitrogen). That would allow you to run both fuel with lower octane and more spark advance than without.

Also, I have my doubts that EGR is fully used for FE savings, since as you approach the maximum amount of EG you can have in the cylinder before you cause a "missing" condition, driveability suffers (appearing as hesitation on acceleration). I believe engineers always err on the side of drivability over efficiency.

A relatively simple & crude way to test this would be to get one of those long exhaust hoses the mechanics use, and set it up to feed exhaust into the intake while driving and monitoring the ScanGauge.

This is an artifact of testing methods, not an actual difference.
See Octane rating - Measurement methods.

Where are you going to pick this up from?

Um.. Not actually planning any test.

But, pick up what?

Sorry, I was wondering where you would pick the exhaust gas up from to take to the intake.

Crap Again
 

Crap again. I was always convinced that the actual anti-knock was higher there, where it's apparently the same -- the whole RON and MON deal. I looked it up in two other spots, so I stand corrected, again. You hear something so many times without the actual data, you become easily convinced. Thanks for the correction :)

One point -- Xylene was not mentioned. Of all of the additives, it seems to have the least "side effects" on the fuel system (if you add lubrication -- such as "Marvel Mystery Oil").

RH77
"making a note to have citations for future posts"

Simplest (for testing) would be the exhaust tip at the back of the car, and a long *** hose back to the front :)

If it worked, then you could look at splicing into a pipe in/near the engine compartment, or modding the EGR valve/system itself (though from what I've read, that'll likely cause the ECU to throw codes).

911 Intervention, Police/Fire/Ambulance
 

But make certain to let the neighbors know that you're not trying to commit suicide :eek: or else expect the whole brigade to show up.

RH77

I was under the impression you couldn't really do that any more with a modern car in good condition. :confused: One of the ways of the 3-way catalyst is to rid the exhaust of the carbonium monoxodyl.

Still, the neighbours might not know this, so the brigade may show up anyway.

I wonder if they'd chase you down the highway while doing tests...

LOL...

I'm still pretty sure that the exhaust byproducts will bind to the body's Oxygen molecules and render the same effects...but I'll have to check on that...not with testing, that's for sure!

RH77

Still Possible, but would take longer
 

OK, the advent of the advanced CATs will slow the process, but there is always unburned fuel present which does it.

From the American College of Chest Physicians.

If inclosed in a garage, the o2 ratio will cause emission levels to increase because the car is using up the oxygen, so more fuel is added until it stalls -- by that time it's too late. If the car isn't breathing by that point, neither would the victim.

RH77

Of course, there is another insidious chemical in automobile exhaust: dihydrogen monoxide. Historically, more people have been killed by this chemical than any other. This is a FACT.

Where is EPA, NHTSA and OSHA on this issue?????

OMG, I just looked it up -- it turns out that it's the main component in Cancer cells, people use it on their yards, and it's even been found in bottled drinks!

;)

RH77

MetroMPG, from what I've gathered, the appropriate amount of EGR reduces peak flame temperatures/NOx during combustion because it minimizes the amount of oxygen in the combustion chamber, but it has limits because if too much exhaust/heat goes back into the cylinder, the fuel will ignite on it's own after hot spots start to develop. So it's a fine line to walk so to speak, fuel with higher octane allows for more EGR, which reduces pumping losses by a proportional amount while resisting detonation that would happen if gasoline was used.

I wonder what makes higher cylinder temperatures: lean burn, or high rates of EGR.

It probably depends in head/cylinder design. I've seen Honda mention swirl during lean burn so they don't get hot spots in the cylinder, and EGR may be able to have the same effect, but in either event, the limiting factor is how much heat can be released in the cylinder before the fuel starts detonating, which should be pretty lose wrt lean burn/EGR in any given engine design.

I'm thinking that the ignition timing will be retarded with the added heat -- and depending on if the vehicle has a knock sensor. If I understand correctly, if you use the proper fuel and introduce more EG, power will decrease, and FE increase? I'm guessing that the temp of the engine would continue to increase with the lean burn and require heavy-duty cooling.

RH77

Not sure if you're saying this, Rick, but EGR isn't lean burn.

With EGR, the air/fuel mixture would remain at stoich (in closed loop via the O2 sensor). It's just that with EGR active, there's less o2 in the intake charge as a proportion of total air mass, so less fuel is introduced. Then, yes, less power, and a wider throttle to compensate, with reduced pumping losses (theoretically).

Not the formal term
 

Darin, I'm trying to wrap my brain around this after a long day, and probably can't offer much but uneducated inquiries -- I figured that Stoich is always the goal of the emissions system (unless in open loop) so the term "Lean Burn" should be described as a Leaner Fuel Mixture when adding an abnormally larger EG recirc. This could result in higher IATs, in leaner mixes, the higher risk of detonation, and consequently higher temps within the combustion chamber. When the ECU finds out that the lean situation is occuring does it not dump more fuel in the charge to cool things down? So in some cases the oxygen and knock sensors report to the ECU to change timing, etc. So multiple factors have to be executed to get this complicated system in good working order for optimum FE. Simply, the whole ECU would need to be replaced or reprogrammed to handle the variables. BTW, does it vary where the EG is entered into the system among vehicles -- I assume directly into the intake manifold in most/all cases?

RH77

Actually, I found a Intro
 

Sorry about the previous rambling post -- no need to answer

I found an introduction to emission basic knowledge that I lack...

How Emissions Systems Work

I've been under the hood trying to find these items and contemplating the alteration of them for better FE/emissions, but I think Honda already figured that out when the car was made.

RH77

"The automaker got it right" doesn't necessarily apply to all areas of design or tuning.

Witness the transmission issue. The people who've done swaps all get better FE than was originally spec'd by the automaker, though at the expense of drivability (that's a subjective term) - maybe acceleration is a better measurement.

I have no idea if higher levels of EGR will actually help FE. Still, I'd be reluctant to say the manufacturer has gone to the limit in that regard.

Soul Searching
 

Honestly, I'm learning here -- I had no idea what the evap canister did until today, and why the emissions routing sticker is present. I've gotten under the hood and found stuff I didn't know was there, and some that I have no clue what it does. I think I found the EGR valve, but I'm not sure. I learned this week that my hot air intake wasn't effective, but counter-effective to a degree. I finally found the starter, which I'll probably have to replace with all of the CODFISHing. No complaints -- trial, error, learning, and sacrifice for the betterment of FE and emissions. That's why I'm here.

The automaker did a good job, but perhaps "right" is too strong of a word. For us, I agree that rarely anything stock is perfect for our applications, but regarding the emission as the final product out of the tailpipe, I realized "how can we be certain that any modification to this system isn't going to hurt and not help". NOx is nasty for Asthmatics, CO2 is ruining our atomosphere, and some automakers are have done a good job and designed longevity into their emissions systems, and others haven't. We can attempt to master FE and use the Scientific Method as our guide to make changes and confirm results. Regarding the EGR...

I think I got over my head in this discussion and I'm asking questions that I could have looked up. I think I'll step aside let you guys take it from here.

-Rick H.

Me too. I'm no expert. My interest in FE, spurred on by this site, has resulted in a lot of unintended education. :)

Good point. I'm willing to take a driveability "hit" for better FE. Which is saying a lot given what I'm driving.

I agree with your points on emissions. We could all find ways to hack our cars to lean out the A/F mixtures and gain MPG, but we'd be increasing oxides of nitrogen in the exhaust. With carb'd cars, you just had to introduce a vacuum leak between the carb and the cylinders.

---

Another bit of EGR / MPG info:

Air induction, EGR, and fuel economy (John De Armond; Bob Hale)
https://yarchive.net/car/air_induction.html

Thanks for the info...
 

Many of us here would disagree. :)

Unintended, but that's a good thing.

Bingo. I've been trying to de-tune my car for better FE. I'll take a huge hit in power if I have to. 145hp is too much for the Integra, and 200+ is a lot for the TSX, but it's starting to get the mileage of the 'Teg, with LEV status. :confused: I admittedly lack any knowledge of the how the Honda K24 engine and its TbW system works. Much more complicated than '98 emissions components.

Something I didn't realize until the last month or so.

Thanks for the link -- I'll dive in and see what happens.

Honestly, I've made some careless errors in posts lately, mostly because I'm home this week, have more time to post and just plain didn't have the facts straight. It's like cramming for an exam -- the brain is designed to actively forget, but when you put too much information into it, what's lost isn't up to the person.

RH77

I've posted this before, and when using a 1.9L TDI modified for SI and PFI, the maximum EGR rate was ~50%, and peak BTE ~43% on methanol, and ~41% on ethanol, which is much better than the Prius' 37%, and more importantly, on ethanol 38% efficiency is seen as low as ~7 bar from ~1.2-1.8k rpm (fig.4), which means that efficiency is ~1.5 times that of the best gasoline engine available during he EPA highway cycle.

Since the price of E85 seems to correspond to it's lower energy rating per gallon, this implies that a Prius powered by one of these engines, running on E85, would probably get ~55mpg of E85 on the EPA highway cycle, or a fuel content adjusted rating of ~77mpg. So as long as the price of E85 is less than 87 octane gas, it would be more efficient, and definitely cheaper, to have this type of engine.

It appears that the limit in terms of minimizing pumping losses via EGR is primarily engine design, and then probably the octane of the fuel. Is anyone else thinking about an intercooled EGR valve? :D

edit- Oh wait, the University of Wisconsin already did for some parallel diesel hybrid project. But no mention of it's use for gassers, I wonder why...

No EGR!
 

Holy guacamole, I just found something out, the TSX has NO EGR!

About the K24 engine...

Quote from:

https://www.vtec.net/articles/view-ar...icle_id=401733

"Cam Timing Mechanism

The biggest gift Honda has given to tuners of the K-series engine is the VTC mechanism. Located on the end of the intake camshaft, the VTC mechanism, via hydraulics, allows 25 [crank] degrees of continuous movement on the TSX and 50 degrees on the RSX. [snip] For emissions, the ability for Honda to rotate the cam to zero at idle to dial out all overlap makes for a very clean engine with no need for EGR. EGR porting is in place on the head, but is blocked off."

I guess that's one way to do it...

RH77

EGR always makes cylinder temperatures lower. That's how it reduces NOx formation.